But nobody seems more arithmetically challenged than the folks who crunch numbers for oil and gas.

For months, the industry estimated that if the feds leased mineral rights on the Roan Plateau, in northwest Colorado, drilling would rake in $1 billion for the state.

“People need to keep their eyes on the $1 billion prize for Colorado, which could be the financial turnaround for the state’s fiscal condition,” harped Greg Schnacke of the Golden-based industry group Americans for American Energy.

But last week, when the Bureau of Land Management auctioned off natural-gas rights on the Roan, it became clear that Colorado’s share would be just $56 million — far less than the windfall Schnacke promised.

I’m no math whiz, but I’m pretty sure they were off by 1,685 percent. Which takes some gall given that a chapter in the industry’s much-touted report on the Roan is titled “Why Analyses by Project Opponents Are Flawed.”

Still shameless about its muddled math, the oil and gas industry continues messing with more numbers — this time in radio and TV ads opposing Initiative 113.

The measure would nix the property tax credit for producers and apply a flat 5 percent severance tax, ending Colorado’s distinction as the highest subsidizing major gas-producing state in the West.

Should voters end the handout, the industry warns that consumers will pay more at the gas pump. That might make sense if Colorado actually produced any significant amounts of oil instead of natural gas and if crude oil weren’t a global commodity.

Gas guys claim in their ads that they employ 71,000 people in Colorado. The state puts that number closer to 25,000.

Out of right field, the gas interests argue that Gov. Bill Ritter’s plan to spend the severance-tax revenues on college scholarships would raise tuition for other students.

By far the lamest of the industry’s tactics is its threat to pack up and leave Colorado should voters up the severance. This comes even though Chevron and British Petroleum have told investors they plan to pump billions of dollars into the state.

We heard such saber-rattling from oil and gas execs earlier this summer when the state began mulling new rules regulating drilling. Their threats sound as hollow as my 5-year-old telling my 3-year-old, “I’m going to ignore you for the rest of my life,” while bickering over the Spiderman spoon they both covet.

Americans for American Energy has rebranded the Roan Plateau as the “U.S. Naval Oil Shale Reserve,” because it sounds, well, more American. AAE’s website also has equated efforts to slow drilling to abetting Iranian President Mahmoud Ahmadinejad and Osama bin Laden, as if wanting to protect Colorado’s air, water and wildlife somehow means you’re a terrorist.

Last year, 10 Western Slope mayors blasted the group for “smear campaigns” and “ruthlessness.”

“You should be ashamed of yourselves,” the mayors wrote.

Oil and gas now is taking aim at Ritter, saying Colorado would have raked in a windfall in Roan revenues had the governor not devalued drilling by voicing doubts about the project.

“He cost the state a cool billion,” Schnacke says, still putting myth over math.

Ritter, for his part, derides industry lackeys for “untethering themselves from the facts.”